The Justice Department reportedly concluded its investigation into unmasking requests made by Obama-era officials without charging anyone involved or releasing a public report on the issue.

Sources told The Washington Post that the investigation, previously led by former U.S. Attorney John Bash, concluded without finding any substantive wrongdoing. While "unmasking" names on classified documents is a common practice, DOJ spokeswoman Kerri Kupec, who revealed the investigation in May, said that month that the frequency of or motive behind Obama-era officials' requests might have been "problematic."

"Unmasking inherently isn't wrong, but certainly, the frequency, the motivation and the reasoning behind unmasking can be problematic, and when you're looking at unmasking as part of a broader investigation -- like [U.S. Attorney] John Durham's investigation -- looking specifically at who was unmasking whom, can add a lot to our understanding about motivation and big-picture events," she said.

The roster featured top-ranking figures including then-Vice President Joe Biden, then-FBI Director James Comey, then-CIA Director John Brennan, then-Director of National Intelligence James Clapper and Obama’s then-chief of staff, Denis McDonough.

REPLACEMENT FOR US ATTORNEY REVIEWING 'UNMASKING' TO ASSUME INVESTIGATIONS: SOURCES

Tuesday's news came after Bash resigned at the beginning of October, leading to Acting U.S. Attorney for the Western District of Texas Gregg Sofer taking his place.

Unmasking occurs after U.S. citizens' conversations are incidentally picked up in conversations with foreign officials who are being monitored by the intelligence community. The U.S. citizens' identities are supposed to be protected if their participation is incidental and no wrongdoing is suspected.

Officials, however, can determine the U.S. citizens' names through a process that is supposed to safeguard their rights. In the typical process, when officials are requesting the unmasking of an American, they do not necessarily know the identity of the person in advance.

The unmasking probe was just one aspect of the Trump administration's attempts, in conjunction with congressional Republicans, to investigate his predecessor's actions. That issue gained traction in recent weeks as Director of National Intelligence John Ratcliffe disclosed that the Obama administration reviewed Russian intelligence on former Democratic presidential nominee Hillary Clinton allegedly attempting to manufacture a controversy surrounding Trump and Russia. 

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Last week, Trump tweeted that he "fully authorized the total Declassification of any & all documents pertaining to the single greatest political CRIME in American History, the Russia Hoax. Likewise, the Hillary Clinton Email Scandal. No redactions!"

While it's unclear how the investigation will proceed, DOJ attorneys reportedly argued in court Tuesday that Trump's tweets didn't constitute official orders to declassify the documents.

Fox News' Brooke Singman and Jake Gibson contributed to this report.